Microwave-enhanced biodiesel method and apparatus

ABSTRACT

A method and a device for the production of biodiesel are disclosed. A suitable bio-feedstock may be exposed to microwave energy during a mixing process, a separation process, and a wash process. A synergistic effect of the microwave energy and centrifugal separation may be used in a continuous process for producing biodiesel. The biodiesel may be produced from the feedstock in a continuous flow path. The microwave energy may enhance the reaction of the feedstock and catalyst to provide a mixture of an ester and glycerin, and the microwave energy may enhance the separation of the ester and the glycerin in a centrifuge. Finally, the microwave energy may enhance the wash process of the ester in a centrifuge to purify the ester to produce a usable biodiesel.

GOVERNMENT RIGHTS

The United States Government has certain rights in this invention pursuant to Contract No. DE-AC07-05-ID14517, between the United States Department of Energy and Battelle Energy Alliance, LLC.

FIELD OF THE INVENTION

Embodiments of the invention relate to devices for use in the preparation of biodiesel fuels and a microwave-enhanced continuous method of making biodiesel. More particularly, in various embodiments, the invention pertains to the application of microwave energy during a mixing process, a centrifuge separation process, and a centrifuge wash process.

BACKGROUND OF THE INVENTION

Biodiesel has been the subject of much investigation as an alternative for petroleum-based diesel fuel. As used herein, the term “biodiesel” refers to an ester-based fuel oxygenate that is derived from a biological source. The biodiesel is used as an alternative for, or as an additive to, petroleum diesel fuel in automobiles or other vehicles. The biodiesel is typically produced from a triglyceride starting material or a fatty acid starting material by a transesterification reaction or an esterification reaction, respectively. Generally, the triglyceride is reacted, or transesterified, with an alcohol to produce glycerol (also known as glycerin) and a corresponding alkyl ester of the triglyceride. Similarly, the fatty acid is reacted, or esterified, with an alcohol to produce a corresponding alkyl ester of the fatty acid. A reaction using methanol as the alcohol forms a methyl ester, and a reaction using ethanol produces an ethyl ester. All such reaction products are referred to commonly herein as an “ester”

Large amounts of the triglyceride and fatty acid starting materials, also referred to as a feed stock, are available from inexpensive sources, such as animal or plant-based fats or oils. Some of these sources are waste food oils. However, since these fats or oils are too viscous to use directly as the biodiesel fuel, the triglycerides or fatty acids are transesterified or esterified to produce the corresponding ester, which has a lower viscosity than that of the starting material. As such, the corresponding ester is suitable for use as the biodiesel fuel.

The transesterification of the triglyceride (or the esterification of the fatty acid) is conducted with an excess of the alcohol in the presence of a catalyst. As the transesterification reaction proceeds, two products are formed, the alkyl ester and the glycerol. One phase includes the alkyl ester and the other phase includes the glycerol. The liquid phases are allowed sufficient time to settle and separate before additional processing steps are conducted to purify the alkyl ester from the glycerol.

Several convention biodiesel production systems of different scale or size are available. Biodiesel may be conventionally produced in either small or large batches. In one conventional small batch method of producing biodiesel, the oil is heated, then mixed with methanol and stirred for two hours. The mixture is allowed to sit for eight hours or more. During this stage, the free fatty acids are esterfied. Sodium methoxide is then added to the mixture, and stirred for an hour. Triglycerids are transesterfied during this step. The final product is washed, and allowed to settle for days. Small batch systems are inefficient, and time-consuming. The process can be technically challenging to operate for the user, and may result in a non-usable product.

Another conventional biodiesel production system is a large scale batch or continuous system. One provider of such a system is Biodiesel Systems of Madison, Wis. These systems require a large capital investment, and require that the oils and fats be collected from remote locations and delivered to the biodiesel production site. Such operations also require dedicated operators or staff.

Therefore it would be desirable to provide a device and method which may be used at the location of the oils and fats, and produces biodiesel more rapidly than the multi-day period of a conventional small batch process and with less in-process feedstock and reagent inventory.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to the production of biodiesel and, in particular, to microwave-enhanced methods and devices for the production of biodiesel.

According to one embodiment of the invention, a biodiesel production device comprises a microwave device configured to provide microwave energy to a chamber thereof; a reaction vessel positioned within the chamber; a first fluid separation apparatus in communication with the reaction vessel and positioned within the chamber; and a second fluid mixing and separation apparatus in communication with the first separation apparatus and positioned within the chamber. An embodiment of the biodiesel production device may be of less than 200 pounds weight and occupy a volume of no more than about nine cubic feet, making it highly portable.

According to another embodiment of the invention, a method of producing biodiesel comprises providing a chamber configured to provide microwave radiation therein; mixing a feedstock and a catalyst within a reaction vessel and subjecting the mixture to microwave energy to form an ester and glycerin mixture; centrifugally separating the ester and the glycerin while applying microwave energy; and washing the ester under the influence of centrifugal force while applying microwave energy.

In still another embodiment of the invention, a system and method of continuously producing biodiesel comprises mixing a feedstock and a catalyst within a reaction vessel having a microwave generation device associated therewith; forming an ester and glycerin mixture in the reaction vessel; separating the ester and the glycerin in a first centrifuge having a second microwave generation device associated therewith; and washing the ester in a second centrifuge having a third microwave generation device associated therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, this invention can be more readily understood and appreciated by one of ordinary skill in the art from the following description of the invention when read in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a schematic drawing of one embodiment of a biodiesel production device of the present invention;

FIG. 2 illustrates a schematic cross-sectional view of one embodiment of a separation contactor of the present invention;

FIG. 3 illustrates a schematic cross-sectional view of one embodiment of a wash contactor of the present invention;

FIG. 4 illustrates portions of another embodiment of a biodiesel production device of the present invention;

FIG. 5 illustrates a schematic drawing of one embodiment of a continuous flow loop of the present invention; and

FIG. 6 shows a cross-sectional view of a rotor assembly of one embodiment of a contactor of the present invention.

DETAILED DESCRIPTION

Embodiments of the invention to biodiesel production devices and, in particular, to devices and methods incorporating microwave energy to esterfy or transesterfy oils and fats and both microwave energy and centrifugal action to rapidly separate and wash the product.

A first embodiment of a biodiesel production device 10 of the present invention is shown in FIG. 1. The biodiesel production device 10 includes a microwave chamber 20. The microwave chamber 20 is configured to provide microwave energy to a volume on the interior thereof. The microwave chamber 20 may comprise, for example, a commercially available microwave oven with some modification thereto, providing inlets and outlets for the materials used in the biodiesel production, and for the finished biodiesel. The microwave chamber 20 may be structured to provide microwave power in the range of 0 to about 5000 Watts. The power range may be adjusted as desired by an operator.

A triglyceride- or fatty acid-containing feedstock suitable for use in forming a biodiesel product may be a liquid, such as a fat, oil, or mixtures thereof. The fat or oil may include, but is not limited to, an animal fat, animal oil, vegetable fat, vegetable oil, or mixtures thereof, such as rapeseed oil, sesame oil, soybean oil, corn oil, sunflower oil, peanut oil, palm oil, palm kernel oil, coconut oil, safflower oil, olive oil, linseed oil, cotton seed oil, tung oil, castor oil, beef fat, pork fat, chicken fat, fish oil, rendered fat, or mixtures thereof. The triglyceride or fatty acid starting material may also be obtained from waste edible oils, such as restaurant grease, household grease, waste industrial frying oil, or mixtures thereof.

A first inlet conduit 30 to the microwave chamber 20 may be in communication with a source of the feedstock for delivery into the biodiesel production device 10. A second inlet conduit 40 may be in communication with a source of catalyst, which may be an acid or base catalyst in alcohol, for delivery into the biodiesel production device 10. For example, the catalyst may be sodium hydroxide, potassium hydroxide, sulphuric acid, or sodium methylate, and an alcohol such as methanol or ethanol. The first inlet conduit 30 and second inlet conduit 40 may join before entering the microwave chamber 20, or within the microwave chamber 20 proximate a reaction vessel 50 disposed within microwave chamber 20, or may feed into reaction vessel independently. The first inlet conduit 30 and the second inlet conduit 40 may be in fluid communication with the reaction vessel, and the catalyst and the feed stock may mix therein. The reaction vessel 50 is desirably transparent to microwave radiation, and microwave energy transmitted to the interior of reaction vessel 50 may be used enhance the reaction between the feed stock and the catalyst by heating. Heating to about 50° C. may be desirable. In addition, the microwave radiation may enhance the synthetic organic transformation and reduce the time needed for the esterfication or transesterification. For example, substantial conversion of the feedstock and the catalyst to an ester and glycerin may take place in about one minute of time in the reaction vessel 50. Liquid transit time through the reaction vessel 50 may be between about 45 seconds and about ten minutes, and the in-process inventory of the reaction vessel may be between about one pint and about two gallons.

The reaction vessel 50 may comprise, for example, an elongated reaction loop of sufficient length for the feedstock and the catalyst to mix, and for the feed stock to be converted, or transesterfied or esterfied, into a corresponding ester. The reaction vessel 50 is desirably transparent to microwave radiation, and may be formed of, for example, a polymer, a plastic, a water-free ceramic, a quartz, a carbon fiber, or a glass.

Static mixers 51 may be included within the reaction vessel 50 to promote mixing of the feedstock and the catalyst. Static mixers 51 may comprise geometric mixing elements fixed within the pipe, which use the energy of the flow stream to mix the feedstock and the catalyst. The static mixers 51 may provide gentle mixing, and ensure a complete and efficient reaction between the feedstock and the catalyst.

The flow rate through the reaction vessel 50 may be modified to ensure adequate conversion. For example, substantial conversion of the feedstock and the catalyst to an ester and glycerin may take place in about one minute of time in the reaction vessel 50 with a flow rate of 1.6 gallons per hour under the application of microwave energy. The volume of the reaction vessel 50 (through adjustment of the length or cross-sectional area) may be predetermined for an adequate conversion at a desired flow rate. Alternatively, the respective rates of introduction of the feedstock and catalyst may be modified to adjust the flow rate for adequate conversion within a reaction vessel 50 having a fixed volume. The configuration of the reaction vessel 50 as a reaction loop enables the transesterfication or esterfication to take place in a continuous process, with the feedstock and the catalyst continuously entering the reaction vessel 50, and a mixture of an ester and glycerin continuously exiting the reaction vessel 50. Following a continuous separation process and wash process, as further described hereinbelow, continuous production of a finished biodiesel product is enabled.

As noted, the mixing and subsequent reaction of the feed stock and the catalyst may form an ester and glycerin combination. By way of example and not limitation, the ester may be a fatty acid alkyl ester, a triglyceride alkyl ester, a methyl ester, an ethyl ester, methyl oleate, or a combination thereof depending on the feedstock and catalyst used. The ester and glycerin combination may be introduced into a separator in the form of first centrifuge 60 and separated therein. The glycerin may be recaptured and recycled in other operations. For example, glycerin may be useful in the food, pharmaceutical or cosmetic industries. The ester may be washed, as described hereinbelow, to form a finished biodiesel product.

The first centrifuge 60 may comprise a liquid-liquid centrifuge for separating the ester and the glycerin. The first centrifuge 60 is desirably transparent to microwave radiation, and may be formed of, for example a polymer, a plastic, a water-free ceramic, a quartz, a carbon fiber, or a glass.

FIG. 2 depicts one embodiment of a first centrifuge 60 of the present invention. The first centrifuge 60 may comprise a centrifuge as disclosed in U.S. Pat. No. 7,150,836 to Meikrantz, entitled “Microwave-Emitting Rotor, Separator Apparatus Including Same, Methods of Operation and Design Thereof,” the disclosure of which is incorporated in its entirety herein. Two commercially available centrifuges having suitable sizes and shapes are the model V02 centrifuge and the model V05 centrifuge, available from CINC Industries of Carson City, Nev. For example, the model V02 centrifuge may have a 2 inch diameter rotor, and the model V05 centrifuge may have a 5 inch diameter rotor.

The first centrifuge 60 may include a housing 12 which may be vertically oriented and may define a generally cylindrical volume which houses a vertically-oriented, substantially cylindrical rotor assembly 14 defined generally by rotor wall 22. Rotor assembly 14 may also include drive shaft 16, weir structure 64, interior shaft 36, walls 42, diverter disk 68 and lower shaft extension 55, each of which may be separable from one another, as known in the art. The drive shaft 16 may be operably coupled to and selectively rotated by a motor (not shown) positioned above the rotor assembly 14, as known in the art. Of course, the rotor assembly 14 may include an upper bearing (not shown) and a lower bearing (not shown) configured for providing support and ease of rotation about a central axis 17 proximate the lower shaft extension 55 and drive shaft 16, respectively.

The housing 12 may include an inlet 62 through which, during operation, the ester and glycerin combination may be introduced from the reaction vessel 50. The combination or mixture may be introduced through an inlet 62 into an annular region 18 defined between the outer radial surface of the rotor sleeve 21 and the inner radial surface of the housing 12. The rotor sleeve 21 may be configured to be stationary with respect to the inner surface 13 of the housing 12. Such a configuration may reduce additional mixing of the constituents of the mixture as it flows within annular region 18. Alternatively, the first centrifuge 60 may not include a rotor sleeve, and the outside surface 15 of the rotor assembly 14 may be in contact with the mixture to promote mixing within the annular region. If the reaction forming the ester is complete when the mixture enters the first centrifuge, no added mixing is desired and a rotor sleeve 21 will preferably be included. The flow of the mixture through the annular region 18 may proceed generally vertically downwardly from the inlet 62 and toward a plurality of radial vanes 26.

The radial vanes 26 may be affixed to housing 12 and may be configured for directing the mixture toward a rotor inlet aperture 34. The radial vanes 26 may extend substantially radially outwardly from the central axis 17 of the rotor assembly 14 toward the inner surface 13 of the housing 12 or, alternatively, may extend along an arcuate path in a generally radially outward fashion from the central axis 17 of the rotor assembly 14 toward the inner surface 13 of the housing 12. Such a configuration may reduce turbulent mixing of the constituents of the mixture passing along the radial vanes 26.

The mixture may continue past the radial vanes 26 and flow into the rotor inlet aperture 34 of the rotor assembly 14. Since the rotor sleeve 21 may be stationary, while the adjacent rotor assembly 14 rotates, an annular seal (not shown) may be provided therebetween, as known in the art. Further, the mixture passing into the rotor inlet aperture 34 of the rotor assembly 14 may encounter a diverter disk 68. Of course, one or more additional sealing elements (not shown), which may comprise dynamic sealing elements or static sealing elements, may be included within the first centrifuge 60 as known in the art. For instance, sealing elements may inhibit the mixture from contact with a motor (not shown), an upper bearing (not shown), or a lower bearing (not shown).

Generally, the rotor assembly 14 may define a generally annular volume which is defined between interior shaft 36 and the inner radial wall 22 of rotor assembly 14. The annular volume may include one or more chambers 32, which may be defined, at least in part, by one or more walls 42 in combination with rotor wall 22, as described hereinbelow in greater detail. Such a configuration may provide increased surface area for interaction with the mixture passing through the rotor assembly 14.

The one or more chambers 32 may comprise at least three chambers for distributing the weight of the mixture and its constituents passing therethrough substantially uniformly during rotation of the rotor assembly 14. In addition, the walls 42 may be oriented substantially vertically or as otherwise desired for forming at least a portion of the one or more chambers 32.

Once the mixture is admitted into the interior of the rotor assembly 14, the centrifugal force of rotation thereof, at generally any desired rotation speed, may cause a constituent of the mixture having a higher density, the glycerin, to be forced outwardly against the inner radial wall 22 of the rotor assembly 14. By way of example and not limitation, the rotor assembly 14 may be configured to rotate at speeds of up to 5000 revolutions per minute, between about 1700 and about 5000 revolutions per minute. A smaller rotor unit may rotate faster than a larger rotor unit to generate sufficient g-force for adequate separation. Thus, a constituent of the mixture having a lower density, the ester, may be displaced radially inwardly toward the interior shaft 36 by the higher density constituent, the glycerin. As may be appreciated, the separation of two liquids having different densities may be effected by operation of the first centrifuge 60 due to the forces developed by rotation of the rotor assembly 14. The synergistic effect of the application of microwave energy and the rotation forces of the first centrifuge 60 may enhance the separation of the ester and the glycerin.

The constituent having a lesser density and the constituent having a greater density may be individually expelled from the housing 12 through exit ports 24 and 28, respectively. More particularly, the ester, having a lesser density, may proceed through the weir structure 38, which may be positioned generally proximate the interior shaft 36, and through the exit port 24 to the outlet path 80 (FIG. 1). The glycerin, having a greater density, may proceed through the weir structure 64 via underflow structure 66, which may be positioned generally proximate to the rotor wall 22 of the rotor assembly 14, and through the exit port 28 to the outlet path 70 (FIG. 1).

The microwave radiation provided in the microwave chamber 20 may heat the mixture, causing the viscosity of the mixture to go down. The individual constituents, the ester and the glycerin may each coalesce more efficiently as the viscosity decreases. Therefore, the microwave radiation may speed the separation of the constituents. In addition, the microwave radiation is preferentially absorbed by the aqueous phase and thus vibrates the aqueous molecules within the mixture, disrupting the surface tension and promoting coalescence. Thus, there is a synergistic effect from the combination of the microwave heating, the application of microwave energy, and the rotational forces of the first centrifuge 60. The separation may take place in as little as 5-30 seconds in the first centrifuge 60. Liquid transit time through the first centrifuge 60 may be between about 10 seconds and about 30 seconds, and the in-process inventory within first centrifuge 60 may be between about 0.4 pints and about ½ gallon. A longer liquid transit time is also within the scope of the present invention. With a higher in-process inventory, the liquid transit time may be the same, but the flow rate will be correspondingly higher.

Turning back to FIG. 1, the glycerin may exit the first centrifuge 60 and the microwave chamber 20 via an outlet path 70. The ester may exit the first centrifuge 60 via outlet path 80 for subsequent introduction into a second mixer and separator in the form of centrifuge 90 for washing.

The second centrifuge 90 may have a first inlet 92 for receiving the ester from outlet path 80. The ester may be washed in centrifuge 90 with a washing agent, for example, an acid or water, to remove traces of reactant, which may corrode an engine when the biodiesel is used. Remaining free glycerin and other impurities may also be removed from the ester. A second inlet 94 is provided to introduce the washing agent from a conduit 85 into the second centrifuge 90. The wash waste may exit the second centrifuge 90 and the microwave chamber 20 via an outlet path 100.

The second centrifuge 90 may comprise a “contactor” centrifuge for mixing and separating the washing agent and the ester. The second centrifuge 90 may be transparent to microwave radiation, and may be formed of, for example a polymer or plastic. FIG. 3 depicts one embodiment of a second centrifuge 90 of the present invention. The second centrifuge 90 may comprise a centrifuge similar to the first centrifuge 60, depicted in FIG. 2. Elements common to FIGS. 2 and 3 retain the same numerical designation. The housing 12 of the second centrifuge 90 includes a first inlet port 92 and a second inlet port 94. The ester may be introduced through the first inlet port 92 and the washing agent may be introduced through the second inlet port 94. The washing agent and the ester may mix in the annular region 18 defined between the outer radial surface of the rotor sleeve 21 and the inner radial surface of the housing 12. The rotor sleeve 21 of the second centrifuge 90 may be employed to limit mixing in the annulus. Alternatively, the second centrifuge may not include a rotor sleeve 21, and the outside surface 15 of the rotor assembly 14 may be in contact with the mixture to promote mixing within the annular region. The shear created in the two liquids trapped between the spinning rotor 14 and the stationary housing 12 enables full mixing. Remaining catalyst, free glycerin, aqueous by-products, reactant and other impurities will dissolve in the washing agent.

The phases of the mixture, that is, the purified ester and the washing agent with the dissolved impurities, may be separated in the interior of the rotor assembly 14. The centrifugal force of rotation of the rotor assembly 14 may cause a constituent of the mixture having a higher density, the washing agent, to be forced outwardly against the inner radial wall 22 of rotor assembly 14, and proceed through the weir structure 64 via underflow structure 66, and through exit port 28 to outlet path 110 (FIG. 1). The purified ester, having a lesser density, may proceed through weir structure 38, which may be positioned generally proximate interior shaft 36, and through exit port 24 to outlet path 100 (FIG. 1).

The combination of the microwave energy and the g-force provided by the centrifuge may increase the output over a conventional washing apparatus by 20-400%. The microwave energy may cause the interface between the washing agent and the ester to resolve faster. The washing may take place in as little as 20-30 seconds in the second centrifuge 90. Liquid transit time through the second centrifuge 90 may be between about 10 seconds and about 30 seconds, and the in-process inventory is about 0.4 pint to ½ gallon, depending on centrifuge size. A longer liquid transit time is also within the scope of the present invention.

Additional wash centrifuge contactors may be added to the cycle for additional purification. For example, as shown in FIG. 4, a biodiesel production device 10′ may include a first centrifuge 60 configured for the separation phase, and three wash centrifuge contactors 90A, 90B, 90C, in series. The centrifuge contactors 60, 90A, 90B, and 90C may all be positioned within a microwave chamber, along with a reaction vessel (not shown) as previously described. A feedstock and a catalyst may be mixed in the reaction vessel to form an ester and glycerin mixture, which may be separated in the first centrifuge 60, as described hereinabove. The ester may exit the first centrifuge 60 and be introduced to the first wash centrifuge contactor 90A via an outlet path 80. The ester may be washed, as described herein above, within the first wash centrifuge contactor 90A. The washing agent may be introduced via inlet path 94A. The once-washed ester may be introduced into the second wash centrifuge contactor 90B, and washed again with a fresh washing agent, introduced via inlet 94B. The twice-washed ester may be introduced into the third wash centrifuge contactor 90C, and washed again with a fresh washing agent, introduced via inlet 94C. The outlets for the spent washing agent from the three wash centrifuge contactors 90A, 90B, 90C are not shown. Each successive washing may be used to further purify the ester. Multiple wash stages may ensure that the biodiesel meets American Society for Testing and Materials (ASTM) and other specifications for biodiesel.

A biodiesel production device 10 or 10′ may have a liquid transit time through the between about one minute and about 30 minutes, and the in-process inventory within the device 10 or 10′ may be between about one gallon and about 10 gallons. The biodiesel production device 10 or 10′ may be transportable, and automated for ease of use. Thus, such a biodiesel production device may be employed at a location of waste oils, for example, at a fast food restaurant. Conversion efficiency with the application of microwave energy may exceed 95%. Thus, a small scale device requiring a low capital investment may be used by a non-technical operator to produce fuel from waste food oil. In one embodiment, the device may be less than nine cubic feet in volume, and weigh less than 200 pounds. For example, a biodiesel production device including first and second centrifuges 60, 90 having two inch diameter rotors may weigh less than 200 pounds. The device 10 or 10′ including centrifuges with about two inch diameter rotors may be used to continuously produce biodiesel at a rate of between about 1 gallon per hour to about 12 gallons per hour, depending on the flow rate.

It is also within the scope of the present invention that the biodiesel production device be between about 200 and about 1000 pounds, and occupy a volume of about nine to about 150 cubic feet. For example, biodiesel production device including first and second centrifuges 60, 90 having five inch diameter rotors may weigh about 1000 lbs, occupy 150 cubic feet. The rate of biodiesel production from such a device 10, 10′ may be between 30 and 150 gallons per hour, depending on the flow rate. Thus, by way of example, a biodiesel device having a production rate of between about 1 gallon per hour to about 150 gallons per hour is within the scope of the present invention.

The microwave enhanced continuous process of the present invention may also be employed on a large scale. Turning to FIG. 5, the microwave energy may be applied to individually to a reaction vessel 150, and to a first and second separation apparatus such as a centrifuge 160, 190. The reaction vessel 150 may comprise a slab tank, enabling even heating. Microwave energy may be applied in the rotor assembly 14 of the first and second centrifuge 160, 190, as shown in FIG. 6. The microwave energy (i.e., microwaves) may be communicated within one or more chambers 32 of the rotor assembly 14 of the first and second centrifuges 160, 190. Such a configuration may enhance or facilitate disengagement or disruption of the forces which form emulsions or dispersions. Accordingly, such a configuration may promote separation of the ester and the glycerin, or the ester and the washing agent. The presence of relatively high centrifugal forces in combination with microwave interaction may enhance the separation of the liquid-liquid mixture. That is, separation of dispersions, emulsions, or both may be promoted by exposure thereof to microwave radiation while under the influence of centrifugal force associated with the rotation of the rotor assembly 14.

The rotor assembly 14 of the first and second centrifuges 160, 190 of the present invention may include at least one microwave generation device for generating microwaves to be communicated therein. Microwave energy may be generated by a microwave generation device 120 positioned generally within the interior shaft 36 and configured for communication of microwave energy into a mixture or its constituents flowing through each of the chambers 32 of the rotor assembly 14. The microwave generation device 120 may comprise any device capable of generating microwaves. For example, the microwave generation device 120 may comprise a maser, a klystron, or a magnetron tube.

Thus, microwave energy may be generated generally within the interior shaft 36. The microwave generation device 120 may extend longitudinally within interior shaft 36. The first and second centrifuges 160, 190 may have rotors of 10 inch diameter or more, and may spin at about 1,000 to about 3,000 rpm.

Another embodiment of the microwave-enhanced diesel production method of the present invention is a continuous flow 105 including a reaction vessel 150 having a microwave generation device 155 associated therewith, a first separation apparatus such as the first centrifuge 160 having a microwave generation device 120 associated therewith, and at least a second mixing and separation apparatus such as the second centrifuge 190 having a microwave generation device 120 associated therewith. The first centrifuge 160 and the second centrifuge 190 may each include a rotor 14 and microwave generation device 120 as shown in FIG. 5. A feedstock 130 and a catalyst 140 may be continuously introduced into the reaction vessel 150, and may react therein to form a mixture of glycerin and an ester. The mixture 157 may be introduced into the first centrifuge 160, and separated therein. The glycerin 162 may exit the system. The ester 165 may be introduced, along with a washing agent 192, into the second centrifuge 190. The ester 165 and the washing agent 192 may be mixed and then separated in the second centrifuge 190, with the washing agent 194 containing impurities removed from the purified ester 196 exiting the system, and the purified ester exiting the system to be used as biodiesel. The reaction or separations may be enhanced by the application of microwave energy in the reaction vessel 150 and in each centrifuge 160, 190. Thus, a purified ester 196 may be continuously produced.

Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some embodiments of the present invention. Similarly, other embodiments of the invention are contemplated and may be devised that do not depart from the spirit or scope of the present invention. Features from different embodiments may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims, are to be embraced thereby. 

1. A biodiesel production device, comprising: a microwave device configured to provide microwave energy to a chamber thereof; a reaction vessel positioned within the microwave chamber; a first separation apparatus in communication with the reaction vessel and positioned within the chamber; and at least one second mixing and separation apparatus in communication with the first separation apparatus and positioned within the chamber.
 2. The biodiesel production device of claim 1, wherein the reaction vessel includes static mixers.
 3. The biodiesel production device of claim 1, wherein the first separation apparatus comprises a first centrifuge configured for initial separation of an ester and glycerin.
 4. The biodiesel production device of claim 3, wherein the first centrifuge further comprises: a first outlet for a first, denser material and configured to remove the first, denser material from the chamber; and a second outlet in communication with the second mixing and separation apparatus.
 5. The biodiesel production device of claim 1, wherein the at least one second mixing and separation apparatus is a second centrifuge comprising: an inlet in communication with an outlet of the first centrifuge; an inlet for a washing agent; a first outlet for a first, denser material and configured to remove the first, denser material from the second centrifuge and from the chamber; and a second outlet.
 6. The biodiesel production device of claim 1, wherein the reaction vessel, the first separation apparatus, and the at least one second mixing and separation apparatus are substantially transparent to microwave energy.
 7. The biodiesel production device of claim 1, wherein the reaction vessel, the first separation apparatus, and the at least one second mixing and separation apparatus comprise at least one of a polymer, a plastic, a water-free ceramic, a quartz, a carbon fiber, and a glass.
 8. The biodiesel production device of claim 1, wherein the biodiesel production device weighs less than 200 pounds and occupies a volume of no more than about nine cubic feet.
 9. The biodiesel production device of claim 1, wherein the reaction vessel, the first separation apparatus, and the second mixing and separation apparatus are mutually configured in a continuous flow path therethrough.
 10. The biodiesel production device of claim 9, wherein the continuous flow path is configured to produce between about 1 gallon per hour to about 12 gallons per hour of biodiesel.
 11. The biodiesel production device of claim 10, wherein the continuous flow path is configured to accommodate an in-process inventory of between about one gallon and about five gallons.
 12. The biodiesel production device of claim 1, wherein the at least one second mixing and separation apparatus is a second centrifuge comprising: a housing; a rotor disposed within the housing; an annular region defined by an inner wall of the housing and an outer wall of the rotor, and in communication with a first and a second inlet; and a chamber disposed within the rotor and configured to separate a first material from a second, denser material.
 13. The biodiesel production device of claim 1, wherein the at least one second mixing and separation apparatus comprises at least two mixing and separation apparatuses configured in a series.
 14. A method of producing biodiesel, comprising: mixing a feedstock and a catalyst while applying microwave energy thereto to form an ester and glycerin mixture; centrifugally separating the ester and the glycerin while applying microwave energy thereto; and centrifugally mixing the ester with a washing agent and centrifugally separating a washed ester from the washing agent while applying microwave energy thereto.
 15. The method of claim 14, wherein the mixing the feedstock and the catalyst comprises introducing the feedstock and the catalyst into a reaction loop.
 16. The method of claim 14, wherein providing a feedstock comprises providing at least one animal- or plant-based fat feedstock or oil feedstock.
 17. The method of claim 16, wherein providing at least one animal-based or plant-based fat feedstock or oil feedstock comprises providing an animal fat, animal oil, vegetable fat, vegetable oil, restaurant grease, household grease, waste industrial frying oil, or mixtures thereof.
 18. The method of claim 14, wherein mixing the ester and the washing agent is effected in an annular region between a spinning rotor and a stationary housing of a centrifuge.
 19. The method of claim 18, wherein separating from the washing agent is effected within the spinning rotor of the centrifuge.
 20. A method of producing biodiesel, comprising: mixing a feedstock and a catalyst within a reaction vessel while applying microwave energy thereto from a microwave generation device associated therewith to form an ester and glycerin mixture in the reaction vessel; separating the ester and the glycerin in a first centrifuge while applying microwave energy thereto from a second microwave generation device associated therewith; and washing the ester in a second centrifuge while applying microwave energy thereto from a third microwave generation device associated therewith.
 21. The method of claim 20, wherein separating the ester and the glycerin in a first centrifuge while applying microwave energy thereto comprises applying the microwave energy from the second microwave generation device positioned within an interior shaft of the first centrifuge.
 22. The method of claim 21, further comprising providing the second microwave generation device selected from the group consisting of a maser, a klystron, and a magnetron.
 23. The method of claim 20, wherein washing the ester comprises mixing the ester and the washing agent in an annular region between a spinning rotor and a stationary housing of a centrifuge.
 24. The method of claim 23, wherein washing the ester further comprises separating the ester from the washing agent within the spinning rotor of the centrifuge.
 25. A biodiesel production system, comprising: a reaction vessel having a first microwave device configured to provide microwave energy to the reaction vessel; a first separation apparatus in communication with the reaction vessel and having a second microwave device configured to provide microwave energy thereto; and a second mixing and separation apparatus in communication with the first separation apparatus and having a third microwave device configured to provide microwave energy thereto.
 26. The biodiesel production system of claim 25, wherein the second microwave device is positioned is positioned within an interior shaft of the first separation apparatus.
 27. The biodiesel production system of claim 25, wherein the third microwave device is positioned is positioned within an interior shaft of the second mixing and separation apparatus. 